Screw plug cap and method of forming the same



Dec. 17, 1957 E. A. TAYLOR SCREW PLUG CAP AND METHOD OF FORMING THE SAME Filed May 12. 1954 FIG.4

FIG.6.

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INVENTORJ ELVIN A.TAYLOR FIG 8;

. ATT QRN EYS United Spires Patent 2,816,681 SCREW PLUG CAP AND METHOD OF FORG THE SAME Elvin A. Taylor, Plymouth, Mich, assignor to Plymouth Stamping Company, Plymouth, MiclL, a corporation of Michigan Application May 12, 1954, Serial No. 429,338 2 Claims. (Cl. 22039) The invention relates to screw caps and more particularly to that type used for retaining a liquid within a container while at the same time providing a vent for the passage of air. One use for such construction is in connection with a master cylinder of a hydraulic brake system.

It is the object of the invention to obtain a construction that can be manufactured at relatively small cost and which provides the necessary vent passage and at the same time forms an eflective baffle for preventing outward passage therethrough of liquid.

It is a further object to obtain a construction having various additional advantageous features.

With these objects in view the invention consists in the construction and method of forming the same as hereinafter set forth.

In the accompanying drawings:

Fig. 1 is a side elevation of my improved screw plug p;

Figs. 2 and 3 are respectively a top plan view and bottom view thereof;

Fig. 4 is a central longitudinal section on line 44, Fig. 3;

Fig. 5 is an enlarged view of a portion of Fig. 4 after the formation of the screw threads thereon;

Figs. 6 and 7 illustrate successive steps in the formation of one of the cup members;

Fig. 8 is a plan view of a modified construction of plug cap;

Fig. 9 is a side elevation thereof;

Fig. 10 is a perspective view.

The plug cap comprises essentially two cupped sheet metal stampings A and B having a central flange union C with each other. The member A has the cupped portion A thereof polygonal, preferably square as shown in Fi 2. A flan e A extends radially from the open end of the cup and is of sufficient extent to form the union C as later described. The member B is formed with a cylindrical cupped portion B with a radial flan e B at its open end. In the st mping of this member it is first formed with an imperforate slightly concaved bottom portion B connected to the cvlindrical side by a rounded portion B The flan e B which is more or less irregular in sha e as first formed is then trimmed to a circular contour of proper diameter and simultaneously with this trimming operation portions of the bottom B are struck out in a downward direction, being severed at the outer edge to form vent slits B with baflie portions B beneath the same. The cylindrical cup portion B is then screw threaded preferably by a rolling thread forming operation which. however, cannot extend completely to the flange B These three operations are all that are required to finish the member B.

To complete the assembly the flange A of the member A which has been trimmed to a circular form and the proper diameter is peened or turned down over the periphery of the flange B and then inward beneath said flange. Thus, the union C forms a radially outwardly extending portion which is equal in thickness to three times the gage of the sheet metal. The inturned por tion A of the flange A will thus cover any unthreaded portion or imperfectly threaded portion of the cylindrical cup B so that the exposed threads will be full throughout their length. The member A is provided at any convenient point with a punched air vent aperture A With the construction as described, the punched out portions B form effective shields for preventing passage of liquid upward into the hollow cap but if any liquid does pass therewithin it will quickly drain out by reason of the convex upper face of the bottom portion B The rounded portion B forms a pilot for guiding the threads of the cap into engagement with those of the casing with which it is engaged. Thus, the cap is easily engaged with the contanier and when tightened Will form an efiEective battle for the liquid content while permitting free air breathing.

Instead of making one of the cupped members poly onal for engagement with a wrench or turning tool, I may form it as shown in Fig. 8 in which the cup member C has a cylindrical portion C of smaller diameter and wing portions C extending diametrically from opposite sides thereof over the radially extending portion C This is adapted to be engaged by the fingers of the hand for screwing it into or out of engagement with the member to be capped instead of requiring a wrench.

What I claim as my invention is:

1. A screw cap comprising two pressed sheet metal cupped members, each having a radially outwardly projecting annular flange at its open end with the flange of one return bent over the other to form a three ply annular abutment the cupped portions of each member extending in the opposite axial direction from the other, one of said members being fashioned to form a hold for the turning of the same, and the other member being generally cylindrical and screw threaded on the outer surface and unthreaded on the inner surface with its bottom portion concave on the exterior and convex on the interior, and a plurality of struck out portions arranged to form narrow segmental slits near the periphery of the concave bottom, whereby any liquid gaining entrance through said slit will drain off from said convex surface and out again through said slits, each of said struck out portions also forming a shield guarding the corresponding slit against entrance of splashed liquid.

2. A plug for retaining a liquid within a container comprising two pressed sheet metal cupped members extending in opposite axial directions, each having a radially outwardly projecting annular flange at its open end with the flange of one return bent over the other to form a three-p ay annular abutment, one of said members having a cylindrical portion extending from its flange with an integral bottom portion convex on the interior and concave on the exterior, the inner surface of said cylindrical portion being smooth and unthreaded, the outer surface of said cylindrical portion being screw threaded from the bottom to said three-ply annular abutment, said integral bottom portion having a plurality of struck out portions forming narrow slits opening at the outer circumference of said convex bottom, and the other of said cupped members having a polygonal portion forming a hold for turning the plug.

References Cited in the file of this patent UNITED STATES PATENTS 1,040,266 Bowen Oct. 8, 1912 1,279,651 Campbell Sept. 24, 1918 1,382,598 Kelly June 21, 1921 1,678,516 Juengst July 24, 1928 1,934,356 Rice Nov. 7, 1933 2,348,452 Christopher May 9, 1944 FOREIGN PATENTS 176,307 Great Britain Mar. 30, 1922 389,592 Great Britain Mar. 23, 1933 149,728 Australia Jan. 27, 1953 

